Millimetre-wave imager detects hidden faults more safely

A millimetre-wave sensor developed by the Fraunhofer Institute is reported to be able to see through all non-transparent materials without emitting harmful rays.

Fraunhofer believes its standalone millimetre wave imager (known as SAMMI) could be used in food production lines to ensure that packets are filled properly and the food itself does not contain impurities.

‘The system detects wooden splinters lurking in nappies, air pockets in plastic, breaks in bars of marzipan and foreign bodies in food. It can even detect and monitor the dehydration process in plants and how severely they have been stressed by drought,’ said Dr Helmut Essen, head of Fraunhofer’s millimetre-wave radar and high-frequency sensors department.

Transmitting and receiving antennas on each of the two opposing rotating plates sit within the system’s housing.

A conveyor belt transports the sample between the antennas while they send electromagnetic waves at 78GHz.

Different areas of the sample absorb the signal to different degrees, leading the varying material composition across a sample to show up in distinguishable contrast.

‘Basically, we examine the scanned objects for dissimilarities,’ explained Essen. The content of the sample appears in real time on the scanner’s foldout display.

The scientists believe that, in the future, the system could be upgraded to terahertz frequencies. ‘Then we’ll be in a position not only to detect different structures but also to establish which type of plastic a product is made from,’ said Essen.

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